Impaired CaSR gene expression is found in parathyroid lesions of both primary and secondary hyperparathyroidism (6-11). No mutations could be found in CaSR gene in parathyroid neoplasias (11,12). Similar present findings shows reduced VDR gene expression (8,13-15) and concur with studies on the apparent lack of VDR gene mutations in hyperparathyroidism (16-18). Differential expression of VDR and CaSR gene has been reported in a few parathyroid adenomas, but exact mechanism is not known. These observations raise the possibility that altered expression of these genes could be related to the pathogenesis of parathyroid adenomas.